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Welcome to TPF!

I stumbled across puffer-ownership 3 months ago and I'm hooked. You get one and before you know it you're afflicted with MTS - multiple tank syndrome. It really is an addiction. Hehe...
Two females and a male sounds good- even better would be 3 females and a male. It gives the male a chance to divide his agressions. I have one male DP and he's quite the character. Usually, he's giving me the sideways glance, and saying "You again?! I find my own food. Stop LOOKING AT ME!"

He's in a 5 gallon hex which has a smaller "footprint" than a rectangular tank, but is okay for just him and a few shrimp. Which brings me to some bad news: I'm afraid your tank is too small for your puffer friends.

Dwarf puffers need 5 gallons for the first one and 3-ish for each additional. That said, I LOVE my 5-gallon. Its small, yes, and they are harder to maintain because of that, but having a little bio-cycle going with fish, shrimp, snails and itty bitty bacteria and moss, and plants is exciting. You just HAVE to keep up with water tests and water changes.
I'm a newbee- only had puffs for 3 months or so. That said, my FIRST puffer was a green spotted (GSP) that I had in this same tank and unfortunately, I killed him. (Too small a tank and too many fish. I'm afraid "Mr. Green" died of severe ammonia poisoning.) You will LOVE this website. Its FRIENDLY and knowlegable. I always feel comfortable with the advice and experience(s) given here, especially when I get confusing or "doesn't-sound-quite-right" from LFS (local fish stores).